This invention relates to hydraulic power converting machines and more particularly to a new and improved multi-vane rotor pump for industrial or power steering use featuring improved undervane hydraulic fluid pressure porting for optimizing undervane pressurization for urging the vanes into operative engagement with the cam surface of an outer cam ring for improving pump operations.
Prior to the present invention various rotary hydraulic vane pumps have been devised with minute and complex hydraulic systems of interconnected pockets, passages and orifices in pump components including the thrust and pressure plates thereof to provide discrete flow paths for coupling the undervane passages with a pump discharge chamber. The hydraulic fluid in the undervane passages is pressurized on pump operation so that the pressurized undervane acts as a hydraulic spring for pump priming and pump operational purposes. More particularly the pressurized undervane fluid acts as a spring to exert a yieldable radial force on the vanes, mounted for reciprocal movement in associated vane slots, to maintain the fluid sealing contact of the tips of the vanes with the associated cam surface during pumping operation.
Examples of such undervane constructions are illustrated and described in U.S. Pat. No. 3,207,077 issued Sep. 21, 1965 to P. B. Zeigler et al for Pump and U.S. Pat. No. 4,386,891 issued Jun. 7, 1983 to R. P. Riefel et al for Rotary Hydraulic Vane Pump With Undervane Passages For Priming.
While such prior art hydraulic pumps have generally met their objectives in providing improved pumping for power steering and other applications, more efficient and effective pumps are needed to meet higher pumping efficiency standards. Moreover, manufacture of prior art pressure and thrust plates with their special and intricately interconnected fluid pockets are difficult and costly. Even with particular attention to detail and care, such construction cannot be readily accomplished by economical manufacturing processes such as casting and stamping operations. Generally such designs require the employment of complex powder metal forming tools and precise machining. Such tooling and procedures makes thrust and pressure plates expensive to produce, particularly where limited quantities are needed
In contrast to the prior art constructions, the present invention provides a new and improved pump which has improved pumping efficiency. This invention incorporates straight forward and simplified vane pressurization porting in the pressure plates that can be readily manufactured by a wide range of processes and equipment including economical stamping and casting. Preferably in this invention a cam ring sandwiched between pressure and thrust plates hydraulically separates the pressure plate from the thrust plate to improve routing of hydraulic pressure fluid to the undervane via special openings in the pressure plate augmenting vane sealing operation. Furthermore, this invention with its improved pressure plate porting for undervane pressurization can be easily employed with a wide range of hydraulic vane pumps including those currently embodied in automotive application as well as transverse compact pumps and hydraulically balanced pump rotors such as disclosed in U.S. Pat. No. 6,050,796 issued to Wong et al. on Apr. 18, 2000 for Vane Pump and hereby incorporated by reference.
Preferably in this invention, a cam ring sandwiched between pressure and thrust plates blocks flow from the discharge ports in the pressure plate to the discharge ports in the thrust plate (and thereby to the pump discharge) to improve pressure routing to the undervane via special inner openings in the pressure plate. More particularly, hydraulic discharge from the pressure plate is primarily through a radial outer port to a sealed undervane pressure chamber at the outboard side of the rotor assembly. Pressure fluid is fed from this side chamber to a pair of interior rotor balancing chambers on opposite sides of the rotor which are hydraulically connected by the undervane passages. With the balancing chambers and the undervane pressurized, the radially extending vanes will be biased by the undervane pressure fluid into operative fluid sealing engagement with the cam surface of the surrounding cam ring.
It is a feature object and advantage of this invention to provide a new and improved rotary vane pump with a flattened pressure plate formed with at least one discharge port for feeding only a side chamber in the pump housing and at least one undervane feed port leading from the side chamber to opposing pressure balancing side chambers of the rotor so that all undervane passages will be pressurized to effect an outward force on the vanes therein for improved engagement of the vanes with an associated outer cam ring.
With the present invention, mechanical noises heretofore generated by some vane pumps will be sharply reduced by the elimination of the arcuate and segmented undervane grooves or other configured undervane recesses or quadrants that may be arranged in various geometric patterns in the faces of the pressure and thrust plates adjacent to the inner ends of the vane slots formed in the pump rotor. These grooves at times formed unintended contact points for any vane tipping in its respective vane groove and projecting out of the side of the rotor. Contact with such grooves by the comer or other parts of the vane resulted in objectionable ratcheting or ticking noises.
In addition to sharply reduced manufacturing costs and reduced noise generation this invention provides improved volumetric efficiency through better sealing between thrust and pressure plates and the rotor sandwiched therebetween.
These and other objects and advantages of the present invention will be more apparent from the following detailed description and drawings in which: